arXiv subjects

Bert Schroer

Publications and source records attributed to Bert Schroer.

At least 37 records · Page 2Linked to original sources

arXiv2012

The foundational origin of integrability in quantum field theory

The main aim of this work is to relate integrability in QFT with a complete particle interpretation directly to the principle of causal localization, circumventing the standard method of finding sufficiently many conservation laws. Its precise conceptual-mathematical formulation as "modular localization" within the setting of local operator algebras also suggests novel ways of looking at general (non-integrable) QFTs which are not based on quantizing classical field theories. Conformal QFT, which is known to admit no particle interpretation, suggest the presence of a "partial" integrability, referred to as "conformal integrability". This manifest itself in a "braid-permutation" group structure which contains in particular informations about the anomalous dimensional spectrum. For chiral conformal models this reduces to the braid group as it is represented in Hecke- or Birman-Wenzl- algebras associated to chiral models. Another application of modular localization mentioned in this work is an alternative to the BRST formulation of gauge theories in terms of stringlike vectorpotentials within a Hilbert space setting.

math-ph↗

arXiv2012

The Einstein-Jordan conundrum and its relation to ongoing foundational research in local quantum physics

We demonstrate the extraordinary modernity of the 1924/25 "Einstein-Jordan fluctuation conundrum", a Gedankenexperiment which led Jordan to his quantization of waves published as a separate section in the famous Born-Heisenberg-Jordan 1926 "Dreimännerarbeit". The thermal nature of energy fluctuations caused by the restriction of the QFT vacuum to a subvolume remained unnoticed mainly because it is not present in QM. In order to understand the analogy with Einstein's fluctuation calculation in a thermal black body system, it is important to expose the mechanism which causes a global vacuum state to become impure on a localized subalgebra of QFT. The present work presents the fascinating history behind this problem which culminated in the more recent perception that "causal localization" leads to thermal manifestations. The most appropriate concept which places this property of QFT into the forefront is "modular localization". These new developments in QFT led to a new access to the existence problem for interacting quantum fields whose solution has remained outside the range of renormalized perturbation theory. It also clarifies open problems about the relation of particles and fields in particular about the incompletely understood crossing property. Last not least it leads to a constructive understanding of integrable versus non-integrable QFTs..

physics.hist-ph↗

arXiv2012

Causality and dispersion relations and the role of the S-matrix in the ongoing research

The adaptation of the Kramers-Kronig dispersion relations to the causal localization structure of QFT led to an important project in particle physics, the only one with a successful closure. The same cannot be said about the subsequent attempts to formulate particle physics as a pure S-matrix project. The feasibility of a pure S-matrix approach are critically analyzed and their serious shortcomings are highlighted. Whereas the conceptual/mathematical demands of renormalized perturbation theory are modest and misunderstandings could easily be corrected, the correct understanding about the origin of the crossing property requires the use of the mathematical theory of modular localization and its relation to the thermal KMS condition. These new concepts, which combine localization, vacuum polarization and thermal properties under the roof of modular theory, will be explained and their potential use in a new constructive (nonperturbative) approach to QFT will be indicated. The S-matrix still plays a predominant role but, different from Heisenberg's and Mandelstam's proposals, the new project is not a pure S-matrix approach. The S-matrix plays a new role as a "relative modular invariant"..

math-ph↗

arXiv2012

Unexplored regions in QFT and the conceptual foundations of the Standard Model

Massive quantum matter of prescribed spin permits infinitely many possibilities of covariantization in terms of spinorial (undotted/dotted) pointlike fields, whereas massless finite helicity representations lead to large gap in this spinorial spectrum which for s=1 excludes vectorpotentials. Since the nonexistence of such pointlike generators is the result of a deep structural clash between modular localization and the Hilbert space setting of QT, there are two ways out: gauge theory which sacrifies the Hilbert space and keeps the pointlike formalism and the use of stringlike potentials which allows to preserve the Hilbert space. The latter setting contains also string-localized charge-carrying operators whereas the gauge theoretic formulation is limited to point-like generated observables. This description also gives a much better insight into the Higgs mechanism which leads to a revival of the more physical "Schwinger-Higgs" screening idea. The new formalism is not limited to m=0, s=1, it leads to renormalizable interactions in the sense of power-counting for all s in massless representations. The existence of stringlike vectorpotentials is preempted by the Aharonov-Bohm effect in QFT; it is well-known that the use of pointlike vectorpotentials in Stokes theorem would with lead to wrong results. Their use in Maxwell's equations is known to lead to zero Maxwell charge. The role of string-localization in the problem behind the observed invisibility and confinement of gluons and quarks leads to new questions and problems. PACS: 11.10.-z, 11.15-q, 11.10Gh, 12.20.-m, 12.38.-t

hep-th↗

arXiv2011

Pascual Jordan's legacy and the ongoing research in quantum field theory

Pascual Jordan's path-breaking role as the protagonist of quantum field theory (QFT) is recalled and his friendly dispute with Dirac's particle-based relativistic quantum theory is presented as the start of the field-particle conundrum which, though in modified form, persists up to this date. Jordan had an intuitive understanding that the existence of a causal propagation with finite propagation speed in a quantum theory led to radically different physical phenomena than those of QM. The conceptional-mathematical understanding for such an approach began to emerge only 30 years later. The strongest link between Jordan's view of QFT and modern "local quantum physics" is the central role of causal locality as the defining principle of QFT as opposed to the Born localization in QM. The issue of causal localization is also the arena where misunderstandings led to a serious derailment of large part of particle theory e.g. the misinterpretation of an infinite component pointlike field resulting from the quantization of the Nambu-Goto Lagrangian as a spacetime quantum string. The new concept of modular localization, which replaces Jordan's causal locality, is especially important to overcome the imperfections of gauge theories for which Jordan was the first to note nonlocal aspects of physical (not Lagrangian) charged fields. Two interesting subjects in which Jordan was far ahead of his contemporaries will be presented in two separate sections.

physics.hist-ph↗

arXiv2010

String theory deconstructed

This essay presents a critical evaluation of the concepts of string theory and its impact on particle physics. The point of departure is a historical review of four decades of ST within the broader context of six decades of failed attempts at an autonomous S-matrix approach to particle theory. The central message, contained in sections 5 and 6, is that string theory is not what its name suggests, namely a theory of of objects in spacetime whose localization is string- instead of point-like. The result is corroborated by the failure of the conformal embedding view: whereas the "target space" of the chiral theory (higher dimensional vector or spinor indices of currents) becomes string theories spacetime, the one-dimensional source space does not describe a string embedded in the target spacetime but rather enriches the "inner" space over each point (spin, masses). Hence string theory solves a problem which enjoyed some popularity in the 60s namely the construction of infinite component fields.

hep-th↗

arXiv2010

An alternative to the gauge theoretic setting

The standard formulation of gauge theories results from the Lagrangian (functional integral) quantization of classical gauge theories. A more intrinsic qunantum theoretical access in the spirit of Wigner's representation theory shows that there is a fundamental clash between the pointlike localization of zero mass (vector, tensor) potentials and the Hilbert space (positivity, unitarity) structure of QT. The quantization approach has no other way than to stay with pointlike localization and sacrifice the Hilbert space whereas the approach build on the intrinsic quantum concept of modular localization keeps the Hilbert space and trades the conflict creating pointlike generation with the tightest consistent localization:: semiinfinite spacelike string localization. Whereas these potentials in the presence of interactions stay quite close to associated pointlike field strength, the interacting matter fields to which they are coupled bear the brunt of the nonlocal aspect in that they are string.generated in a way which cannot be undone by any differentiation. The new stringlike approach to gauge theory also revives the idea of a Schwinger-Higgs screening mechanism as a deeper and less metaphoric description of the Higgs spontaneous symmetry breaking and its accompanying tale about "God's particle" and its mass generation for all other particles.

math-ph↗

arXiv2010

Localization and the interface between quantum mechanics, quantum field theory and quantum gravity II (The search of the interface between QFT and QG)

The main topics of this second part of a two-part essay are some consequences of the phenomenon of vacuum polarization as the most important physical manifestation of modular localization. Besides philosophically unexpected consequences, it has led to a new constructive "outside-inwards approach" in which the pointlike fields and the compactly localized operator algebras which they generate only appear from intersecting much simpler algebras localized in noncompact wedge regions whose generators have extremely mild almost free field behavior. Another consequence of vacuum polarization presented in this essay is the localization entropy near a causal horizon which follows a logarithmically modified area law in which a dimensionless area (the area divided by the square of dR where dR is the thickness of a light sheet) appears. There are arguments that this logarithmically modified area law corresponds to the volume law of the standard heat bath thermal behavior. We also explain the symmetry enhancing effect of holographic projections onto the causal horizon of a region and show that the resulting infinite dimensional symmetry groups contain the Bondi-Metzner-Sachs group.

math-ph↗

arXiv2010

Localization and the interface between quantum mechanics, quantum field theory and quantum gravity I (The two antagonistic localizations and their asymptotic compatibility)

It is shown that there are significant conceptual differences between QM and QFT which make it difficult to view the latter as just a relativistic extension of the principles of QM. At the root of this is a fundamental distiction between Born-localization in QM (which in the relativistic context changes its name to Newton-Wigner localization) and modular localization which is the localization underlying QFT, after one separates it from its standard presentation in terms of field coordinates. The first comes with a probability notion and projection operators, whereas the latter describes causal propagation in QFT and leads to thermal aspects of locally reduced finite energy states. The Born-Newton-Wigner localization in QFT is only applicable asymptotically and the covariant correlation between asymptotic in and out localization projectors is the basis of the existence of an invariant scattering matrix. In this first part of a two part essay the modular localization (the intrinsic content of field localization) and its philosophical consequences take the center stage. Important physical consequences of vacuum polarization will be the main topic of part II. Both parts together form a rather comprehensive presentation of known consequences of the two antagonistic localization concepts, including the those of its misunderstandings in string theory.

math-ph↗

arXiv2010

A critical look at 50 years particle theory from the perspective of the crossing property

The crossing property is perhaps the most subtle aspect of the particle-field relation. Although it is not difficult to state its content in terms of certain analytic properties relating different matrixelements of the S-matrix or formfactors, its relation to the localization- and positive energy spectral principles requires a level of insight into the inner workings of QFT which goes beyond anything which can be found in typical textbooks on QFT. This paper presents a recent account based on new ideas derived from "modular localization" including a mathematic appendix on this subject. Its main novel achievement is the proof of the crossing property of formfactors from a two-algebra generalization of the KMS condition. The main content of this article is the presentation of the derailments of particle theory during more than 4 decades: the S-matrix bootstrap, the dual model and its string theoretic extension. Rather than being related to crossing, string theory is the (only known) realization of a dynamic infinite component one-particle wave function space and its associated infinite component field. Here "dynamic" means that, unlike a mere collection of infinitely many irreducible unitary Poincaré group representation or free fields, the formalism contains also operators which communicate between the different irreducible Poincaré represenations (the levels of the "infinite tower") and set the mass/spin spectrum. Wheras in pre-string times there were unsuccessful attempts to achieve this in analogy to the O(4,2) hydrogen spectrum by the use of higher noncompact groups, the superstring in d=9+1, which uses instead (bosonic/fermionic) oscillators obtained from multicomponent chiral currents is the only known unitary positive energy solution of the dynamical infinite component pointlike localized field project.

math-ph↗

arXiv2010

Bondi-Metzner-Sachs symmetry, holography on null-surfaces and area proportionality of "light-slice" entropy

It is shown that certain kinds of behavior, which hitherto were expected to be characteristic for classical gravity and quantum field theory in curved spacetime, as the infinite dimensional Bondi-Metzner-Sachs symmetry, holography on event horizons and an area proportionality of entropy, have in fact an unnoticed presence in Minkowski QFT. This casts new light on the fundamental question whether the volume propotionality of heat bath entropy and the (logarithmically corrected) dimensionless area law obeyed by localization-induced thermal behavior are different geometric parametrizations which share a common primordeal algebraic origin. Strong arguments are presented that these two different thermal manifestations can be directly related, this is in fact the main aim of this paper. It will be demonstrated that QFT beyond the Lagrangian quantization setting receives crucial new impulses from holography onto horizons. The present paper is part of a project aimed at elucidating the enormous physical range of "modular localization". The latter does not only extend from standard Hamitonian heat bath thermal states to thermal aspects of causal- or event- horizons addressed in this paper. It also includes the recent understanding of the crossing property of formfactors whose intriguing similarity with thermal properties was, although sometimes noticed, only sufficiently understood in the modular llocalization setting.

hep-th↗

arXiv2010

Geometry and Localization, a metaphorically related pair

It is often overlooked that local quantum physics has a built in quantum localization structure which may under certain circumstances disagree with (differential, algebraic) geometric ideas. String theory originated from such a spectacular misinterpretation of a source-target embedding in which an inner symmetry of the source object becomes the Lorentz symmetry of the target space. The quantum localization reveals however that the resulting object is an infinite component pointlike field. There are also other other areas in QFT which suffered from having followed geometrical metaphors and payed too little attention to the autonomous localization properties. This will be illustrated in the concrete context of three examples. We also show that "modular localization ", i.e. the intrinsic localization theory of local quantum quantum physics, leads to a radiacal new way of looking at (nonperturbative) QFT. For the first time in the history of QFT there are now existence theorems for a class of strictly renormalizable (i.e. not superrenormalizable) factorizable QFTs which are based on these new concepts. The paper ends with some worrisome sociological observations about the state of particle physics and the direction in which it is heading. These remarks are based on the results presented in the three previous sections.

physics.gen-ph↗

arXiv2010

Jorge A. Swieca's contributions to quantum field theory in the 60s and 70s and their relevance in present research

After revisiting some high points of particle physics and QFT of the two decades from 1960 to 1980, I comment on the work by Jorge Andre Swieca. I explain how it fits into the quantum field theory during these two decades and draw attention to its relevance to the ongoing particle physics research. A particular aim of this article is to direct thr readers mindfulness to the relevance of what at the time of Swieca was called "the Schwinger Higgs screening mechanism". which, together with recent ideas which generalize the concept of gauge theories, has all the ingredients to revolutionize the issue of gauge theories and the standard model.

physics.hist-ph↗

arXiv2009

A note on Infraparticles and Unparticles

The observed astrophysical phenomenon of dark matter has generated new interest in the problem of whether the principles underlying QFT are consistent with invisibility/inertness of energy-momentum carrying "stuff" as e.g. "unparticles". We show that the 2-dim. model which has been used to illustrate the meaning of unparticles belongs to the class of former infraparticles models and the latter are known to describe electrically charged particles in d=1+3 which despite their nonlocality are our best particle physics "candles". The "invisibility" in this case refers to the infinite infrared photon cloud with energies below the resolution and can be made arbitrarily small by increasing the photon registering sensitivity. This is not quite the kind of invisibility which the unparticle community attributes to their invisible "stuff" and which would probably contradict the asymptotic completeness property. The main aim of the present work is to show that knowledge about this part of QFT is still in its infancy and express the hope that the work on unparticles may rekindle a new interest in conceptually subtle old unsolved important problems.

hep-th↗

arXiv2009

Localization and the interface between quantum mechanics, quantum field theory and quantum gravity

We show that there are significant conceptual differences between QM and QFT which make it difficult to view the latter as just a relativistic extension of the principles of QM. At the root of this is a fundamental distinction between Born-localization in QM (which in the relativistic context changes its name to Newton-Wigner localization) and modular localization which is the localization underlying QFT, after one liberates it from its standard presentation in terms of field coordinates. The first comes with a probability notion and projection operators, whereas the latter describes causal propagation in QFT and leads to thermal aspects of locally reduced finite energy states. The Born-Newton-Wigner localization in QFT is only applicable asymptotically and the covariant correlation between asymptotic in and out localization projectors is the basis of the existence of an invariant scattering matrix. Taking these significant differences serious has not only repercussions for the philosophy of science, but also leads to a new structural properties as a consequence of vacuum polarization: the area law for localization entropy near the the causal localization horizon and a more realistic cutoff independent setting for the cosmological vacuum energy density which is compatible with local covariance. The article presents some observations about the interface between QFT in CST and QG.

hep-th↗

arXiv2008

Indecomposable semiinfinite string-localized positive energy matter and "darkness"

In the absence of interactions indecomposable positive energy quantum matter comes in form of three families of which the massless so called "infinite spin" family which appeared first in Wigner's famous 1939 work is (if mentioned at all) usually dismissed as "unphysical" but without indicating what principle (if at all) is being violated. Using novel methods which are particularly suited for problems of localization, it was shown that these representations cannot be generated by pointlike localized fields but rather require the introduction of string-like generators which are localized along semiinfinite spacelike strings. We argue that such objects can neither be registered in quasilocal Araki-Haag counters nor pair-produced from standard matter. Reviewing the mathematical status of Murphy's law in local quantum physics (everything which is not prohibited to couple does indeed couple) off and on shell, we are led to the result that perfect darkness is only possible in QFT with string-localized fields. PACS: 95.35+d, 11.10-z, 11.30Cp

hep-th↗

arXiv2008

Do confinement and darkness have the same conceptual roots?

In this note the connection between "perfect dark matter" and string-localization as the tightest noncompact localized matter is pursued in the context of Yang Mills theories. A programmatic approach based on the observation that behind the serious infrared problems which prevented the use of the axial gauge there is unique covariant semiinfinite string-like field, which flucuates in the endpoint as well as in the string direction, is formulated and the open problems are explained. Whereas hitherto the gauge formalism in its local gauge invariants accounted for the observed hadrons the new formalism based on the consistent use of string-localized vectorpotentials has a good chance to unravel the nonlocal part in which energy-momentum carrying dark/confined objects (gluons, quarks,..) may be residing. PACS: 95.35+d, 11.10-z, 11.30 Cp

hep-th↗

arXiv2008

String theory and the crisis of particle physics II or the ascent of metaphoric arguments

This is a completely reformulated presentation of a previous paper with the same title; this time with a much stronger emphasis on conceptual aspects of string theory and a detailed review of its already more than four decades lasting history within a broader context, including some little-known details. Although there have been several books and essays on the sociological impact and its philosophical implications, there is yet no serious attempt to scrutinize its claims about particle physics using the powerful conceptual arsenal of contemporary local quantum physics. I decided to leave the previous first version on the arXiv because it may be interesting to the reader to notice the change of viewpoint and the reason behind it. Other reasons for preventing my first version to go into print and to rewrite it in such a way that its content complies with my different actual viewpoint can be found at the end of the article. The central message, contained in sections 5 and 6, is that string theory is not what string theorists think and claim it is. The widespread acceptance of a theory whose interpretation has been obtained by metaphoric reasoning had a corroding influence on the rest of particle physics theory as will be illustrated in several concrete cases. The work is dedicated to the memory of Juergen Ehlers with whom I shared many critical ideas, but their formulation in this essay is fully within my responsibility.

hep-th↗